The present invention relates to a confocal probe to be employed in an endoscope device and a confocal endoscope device for observing tissues inside the human body and the like.
Conventionally, when tissues of a human body are examined, parts of the tissues are cut using a treatment tool such as a forceps for cutting. Then, the cut parts of the tissues are examined. Such an examination requires a relatively long time, and it has been difficult to apply medical treatment quickly.
Recently, a confocal optical scanning probe for non-invasive imaging has been known. Typically, the confocal probe is configured to illuminate tissues inside a human body with a scanning laser beam, and receives a reflected beam that is reflected at a focal point of an objective optical system of the confocal probe. Examples of such a confocal probe are disclosed in Japanese Patent No. 3032720 and No. 3052150.
The confocal probe is configured such that a pin hole is provided, in front of a detector, at a position conjugate with an object-side focal point of the objective optical system. With this configuration, the detector only receives the reflected light, which is reflected by the tissues, at a point on which the light is focused. The detector, which is connected to an image processing unit, receives the reflected light passed through the pin hole, and performs photoelectric transformation.
In order to capture two-dimensional or three-dimensional images of the tissues, the laser beam is scanned on the tissues. For this purpose, the confocal probe is provided with scanning mirrors for scanning the laser beam along two-dimensional directions, or along three-dimensional directions.
Each of the scanning mirrors employed in the confocal probe is formed on semi-conductive material such as a silicon substrate. In a conventional confocal probe, the silicon substrate mounting the scanning mirror is typically secured inside a device with supporting members secured on an inner wall of a main body of the device.
As above, the supporting members are located on an outer side of the scanning mirror (i.e., apart from the optical axis of the probe), in which case, the diameter of the probe tends to be larger. Further, in conventional confocal probes, a plurality of mirrors for scanning a beam in different directions are formed on different silicon substrates. Therefore, the manufacturing process of the scanning mirrors and assembling process thereof tends to be complicated, which may increase manufacturing costs.
The scanning optical system is generally made of glass material such as BK7 or quart glass. The CTE (coefficient of thermal expansion) of the silicon substrate is several ten of times as much as the CTE of the BK7 or quart glass. Therefore, when a relatively large thermal change occurs, a positional relationship of the optical system and the scanning mirrors is shifted, which causes the optical path of the scanning laser beam to be displaced. Due to this relatively worse thermal characteristic of the probe, under a relatively high temperature around the probe, it is difficult to keep a precise location of the image.